1. Field of the Invention
The present invention is related to a method for manufacturing magnetic heads for lapping magnetic head elements in order to make the height of the magnetic heads uniform after the magnetic head elements are formed on a wafer.
2. Description of the Related Art
In a magnetic head manufacturing process, after forming a magnetic head thin film, the magnetic head thin film is lapped. This lapping uniformly processes the gap length and magnetoresistive film of the magnetic head thin film. Sub-micron order precision is required for a magnetoresistive film and gap length.
FIG. 27A and FIG. 27B are schematic drawings of a merged magnetic head.
As shown in FIG. 27A, a merged magnetic head 80 comprises a magnetoresistive element 82 and writing element 85 formed on a substrate 81. As shown in FIG. 27B, the magnetoresistive element 82 comprises a magnetoresistive film 83 and a pair of conductors 84. The resistance value of the magnetoresistive element 82 changes in the presence of an external magnetic field. This magnetoresistive element 82 is a reading element, which outputs a current equivalent in strength to the magnetic force of a track 90 on a magnetic disk.
The magnetoresistive element 82 is only used for reading, requiring that a writing element be fabricated separately. The writing element 85 is configured as an inductive head. The writing element 85 comprises a bottom magnetic pole 86 and a top magnetic pole 88 that faces the bottom magnetic pole 86 across a gap. A coil 87, which excites these magnetic poles 86, 88 is fabricated between the magnetic poles 86, 88. A non-magnetic insulation layer 89 is fabricated around the coil 87.
In a merged magnetic head such as this, the resistance value of the magnetoresistive film 83 of the magnetoresistive element 82 must be constant for each head. However, in a magnetic head thin film manufacturing process, it is impossible to make this resistance value uniform. Consequently, after forming the magnetic head thin film, the magnetic head thin film is subjected to lapping in order to make the height (width) h of the magnetoresistive film 83 uniform thereby making the resistance values uniform.
FIGS. 28A to 29D provide schematic diagrams depicting the manufacturing process for such merged magnetic heads.
As shown in FIG. 28A, thin-film technology is used to form a plurality of merged magnetic heads 102 on a wafer 100. Then, as shown in FIG. 28B, the wafer 100 is cut into strips, creating row bars, (blocks) 101. A row bar 101 comprises one row of magnetic heads 102. And resistance elements 102a for process monitoring are formed on the left end, in the middle and on the right end of the row bar 101.
As explained previously, the magnetic heads 102 are lapped to make the height of the magnetoresistive film 83 uniform. However, the row bar is extremely thin, for example, around 0.3 millimeters. Consequently, it is impossible to mount it directly to the lapping jig. Consequently, as shown in FIG. 28C, a row bar 101 is bonded to a mounting jig (base) 103 using a heat-melted wax.
Then, as shown in FIG. 29A, the row bar 101 is placed on a lapping plate, and subjected to lapping. At this time, as pointed out in Japanese patent disclosure publication number 2-124262 (U.S. Pat. No. 5,023,991) and Japanese patent disclosure publication number 5-123960, the resistance values of the resistance elements 102a for monitoring the processing of the row bar 101 are constantly measured during lapping. Then, these resistance values are used to detect whether or not the magnetoresistive film 83 of the magnetic heads 102 has achieved the target height.
Lapping is terminated when the magnetoresistive film has been processed to the target height by the resistance value measurements. After that, as shown in FIG. 29B, a slider is formed on the bottom surface 101-1 of the row bar 101.
Also, as shown in FIG. 29C, the row bar 101 is cut into individual magnet heads 102 while it is attached to the mounting jig 103. Then, as illustrated in FIG. 29D, each magnetic head 102 is removed by heating the mounting jig 103 and melting the heat-melted wax.
A row bar 101 comprising a row of magnetic heads 102 is prepared in this way, and since lapping is performed in row bar units, the magnetoresistive film of a plurality of magnetic heads 102 can be lapped at the same time.
FIGS. 30A and 30B provides schematic diagrams depicting the prior art.
As shown in FIG. 30A, the row bar 101 comprises magnetic head elements 102 and monitoring elements 102a. The magnetic head elements 102, as described earlier, comprise a magnetoresistive film 83 and terminals 84. The monitoring elements (hereafter referred to as electrical lapping guide (ELG) elements) 102a comprise a resistance film 1020 and terminals 1021. This magnetoresistive film 83 and resistance film 1020 are formed from the same material.
As for this resistance film 1020, as shown in FIG. 30B, the lower the height ELGh of the resistance film 1020, the higher its resistance value. Therefore, the height ELGh of the resistance film 1020 can be detected by measuring the resistance value of the resistance film 1020 of the ELG elements 102a. 
Since the height MRh of the magnetoresistive film 83 of the magnetic heads 102 is practically equivalent to the height ELGh of the resistance film 1020, the height ELGh of the resistance film 1020 is equivalent to the height MRh of the magnetoresistive film 83. This is used to convert the resistance value of the resistance film 1020 of the ELG elements 102a to the height MRh of the magnetoresistive film 83 of the magnetic heads 102.
Further, the magnetoresistive film 83 is formed on the wafer substrate through a shield layer. Conversely, the ELG elements 102a are not used as magnetic heads. Consequently, since a shield is not necessary, the ELG elements 102a are fabricated directly on the wafer substrate.
The following problems occurred with methods like this whereby ELG elements 102a are fabricated on row bar 101, and lapping is controlled by measuring the resistance of the ELG elements 102a. 
Firstly, there were variations in accuracy when aligning masks to wafers. Consequently, the position P0 of the end of the magnetoresistive film 83 shown in FIG. 30A differs slightly from the position P1 of the end of the resistance film 1020. This is roughly a 0.1-0.2 micron difference, and for magnetic heads requiring micron order processing accuracy, this was not a problem.
However, when it comes to maintaining submicron processing accuracy, this difference poses a problem. With prior art, since the height of the ELG elements was treated as equivalent to the height of the magnetoresistive film, and the resistance values of the ELG elements were converted to the height of the magnetoresistive film, an accurate magnetoresistive film height could not be obtained. Consequently, the non-uniformity of the post-processing height of the magnetoresistive film was a problem.
Secondly, because the formation conditions for ELG elements are the same as those for magnetoresistive films, the same process used to fabricate magnetoresistive film was also used to fabricate ELG elements. However, since an ELG element is not fabricated through a shield layer, the distance from the pattern-generating stepper to the ELG element differs from the distance from the stepper to the magnetoresistive film. Consequently, the accuracy of ELG element pattern formation declines. This decline in accuracy increases the difference between the position P0 of the end of the magnetoresistive film 83 and the position P1 of the end of the resistance film 1020.
With prior art, since the height of the ELG elements was treated as equivalent to the height of the magnetoresistive film, and the resistance values of the ELG elements were converted to the height of the magnetoresistive film, an accurate magnetoresistive film height could not be obtained. Consequently, the non-uniformity of the post-processing height of the magnetoresistive film was a problem.
An object of the present invention is to provide a magnetic head manufacturing method for achieving magnetic head elements of uniform height via processing.
Another object of the present invention is to provide a magnetic head manufacturing method for obtaining accurate magnetic head element heights from ELG element resistance values.
Another object of the present invention is to provide a magnetic head manufacturing method for enhancing the alignment accuracy of the ELG elements and magnetic head elements.
FIGS. 1A and 1B are fundamental diagrams depicting the present invention.
The present invention comprises a step for forming on a wafer a plurality of magnetic head elements 102 and monitoring elements 102a incorporating analog resistance, by which resistance values change in analog fashion in line with the processing of the magnetic head elements 102; a step for cutting from the wafer a block 101 in which the plurality of magnetic head elements 102 and monitoring elements are lined up linearly; a step for processing the height of the magnetic head elements 102 to a prescribed height while measuring the resistance values of the monitoring elements 102a in the block 101; and a step for dividing the block 101 into individual magnetic heads 102 following processing.
Then, in one feature of the present invention, as shown in FIG. 1A, the formation step comprises a step for measuring the difference xcex94I in the positions of the ends of the formed monitoring elements 102a and the ends of the formed magnetic head elements 102; and the processing step comprises a step for using the difference xcex94I in positions to convert the resistance values of the monitoring elements 102a to the height of the magnetic head elements 102, and a step for terminating the processing when the height of the magnetic head elements 102 reaches a target value.
In this feature of the present invention, the difference xcex94I between the positions of the ends of the monitoring elements 102a and the ends of the magnetic head elements 102 is measured, and the difference xcex94I between these positions is incorporated into a relational expression that converts the resistance values of the monitoring elements 102a to the height of the magnetic head elements 102. Consequently, even though the resistance values of the ELG elements are converted to the height of the magnetoresistive film, an accurate magnetoresistive film height is obtained. This makes it possible to achieve precision uniformity of height of the magnetoresistive film following processing.
Further, in another feature of the present invention, as shown in FIG. 1B, the formation step comprises a process for fabricating a bottom shield layer 91 on the wafer substrate 100, a process for fabricating an insulation layer 92 on the bottom shield layer 91, and a process for fabricating the magnetoresistive film 83 of the magnetic head elements 102 and the monitoring elements 102a on the insulation layer 92.
In this feature of the present invention, because the monitoring elements 102a are also fabricated on the substrate 100 through the shield layer 91, the distance between the stepper and the monitoring elements 102a and the distance between the stepper and the magnetoresistive film 83 of the magnetic head elements 102 are equivalent. Consequently, the pattern formation accuracy is the same for both the monitoring elements 102a and the magnetic head elements 102.
This reduces the difference between the position P0 of the end of the magnetoresistive film 83 and the position P1 of the end of the resistance film 1020. Therefore, even though the resistance values of the ELG elements are converted to the height of the magnetoresistive film, an accurate magnetoresistive film height is obtained. Consequently, it is possible to achieve precision uniformity of height of the magnetoresistive film following processing.
Other features and advantages of the present invention will become readily apparent from the following description taken in conjunction with the accompanying drawings.